1. Field of the Invention
The present invention relates generally to methods of heating tooling dies. Specifically, the invention relates to a method of heating a tooling die by utilizing a heater element such as, a laminated composite heater element.
2. Description of the Prior Art
The effective use of tooling dies requires that they be maintained at a constant temperature. During idle periods the die will cool. When the manufacturing resumes, the first few items are typically wasted because the tooling die does not adequately reach operating temperature until several cycles are performed. Maintaining the temperature of the tooling die during the idle times can increase production by eliminating the start/restart waste. Thus, it would be desirable to provide a method for maintaining the surface temperature of a tooling die.
A variety of elements for heating surfaces exist in the prior art. U.S. Pat. No. 4,534,886, to Kraus et al., discloses an electrically conductive web comprising a non-woven sheet of conductive fibers and non-conductive fibers. The sheet is saturated with a dispersion containing conductive particles and is then dried. The Kraus et al. heater element is primarily used in heating pads.
International Application No. PCT/US94/13504 (Publication No. WO95/15670), discloses an electrically conductive composite heating assembly that has an electrically conductive non-woven fiber layer laminated between layers of fiberglass and other dielectric material and has an abrasion resistant outer layer. The heater element is used in an ice protection system to withstand repeated mechanical stress and thermal cycles in extremely harsh aerospace applications.
U.S. Pat. No. 5,344,696 to Hastings et al. discloses an integrally bonded laminate which is used to thermally control a surface or portion of a surface of an aircraft to which the laminate is bonded.
However, none of the prior art heater elements have been successfully applied to tooling dies.